Commit 3590ec58 authored Feb 09, 2021 by Ira Weiny Committed by David Sterba Feb 26, 2021

btrfs: use memcpy_[to|from]_page() and kmap_local_page()

There are many places where the pattern kmap/memcpy/kunmap occurs.

This pattern was lifted to the core common functions
memcpy_[to|from]_page().

Use these new functions to reduce the code, eliminate direct uses of
kmap, and leverage the new core functions use of kmap_local_page().

Also, there is 1 place where a kmap/memcpy is followed by an
optional memset.  Here we leave the kmap open coded to avoid remapping
the page but use kmap_local_page() directly.

Development of this patch was aided by the coccinelle script:

// <smpl>
// SPDX-License-Identifier: GPL-2.0-only
// Find kmap/memcpy/kunmap pattern and replace with memcpy*page calls
//
// NOTE: Offsets and other expressions may be more complex than what the script
// will automatically generate.  Therefore a catchall rule is provided to find
// the pattern which then must be evaluated by hand.
//
// Confidence: Low
// Copyright: (C) 2021 Intel Corporation
// URL: http://coccinelle.lip6.fr/


// Comments:
// Options:

//
// simple memcpy version
//
@ memcpy_rule1 @
expression page, T, F, B, Off;
identifier ptr;
type VP;
@@

(
-VP ptr = kmap(page);
|
-ptr = kmap(page);
|
-VP ptr = kmap_atomic(page);
|
-ptr = kmap_atomic(page);
)
<+...
(
-memcpy(ptr + Off, F, B);
+memcpy_to_page(page, Off, F, B);
|
-memcpy(ptr, F, B);
+memcpy_to_page(page, 0, F, B);
|
-memcpy(T, ptr + Off, B);
+memcpy_from_page(T, page, Off, B);
|
-memcpy(T, ptr, B);
+memcpy_from_page(T, page, 0, B);
)
...+>
(
-kunmap(page);
|
-kunmap_atomic(ptr);
)

// Remove any pointers left unused
@
depends on memcpy_rule1
@
identifier memcpy_rule1.ptr;
type VP, VP1;
@@

-VP ptr;
	... when != ptr;
? VP1 ptr;

//
// Some callers kmap without a temp pointer
//
@ memcpy_rule2 @
expression page, T, Off, F, B;
@@

<+...
(
-memcpy(kmap(page) + Off, F, B);
+memcpy_to_page(page, Off, F, B);
|
-memcpy(kmap(page), F, B);
+memcpy_to_page(page, 0, F, B);
|
-memcpy(T, kmap(page) + Off, B);
+memcpy_from_page(T, page, Off, B);
|
-memcpy(T, kmap(page), B);
+memcpy_from_page(T, page, 0, B);
)
...+>
-kunmap(page);
// No need for the ptr variable removal

//
// Catch all
//
@ memcpy_rule3 @
expression page;
expression GenTo, GenFrom, GenSize;
identifier ptr;
type VP;
@@

(
-VP ptr = kmap(page);
|
-ptr = kmap(page);
|
-VP ptr = kmap_atomic(page);
|
-ptr = kmap_atomic(page);
)
<+...
(
//
// Some call sites have complex expressions within the memcpy
// match a catch all to be evaluated by hand.
//
-memcpy(GenTo, GenFrom, GenSize);
+memcpy_to_pageExtra(page, GenTo, GenFrom, GenSize);
+memcpy_from_pageExtra(GenTo, page, GenFrom, GenSize);
)
...+>
(
-kunmap(page);
|
-kunmap_atomic(ptr);
)

// Remove any pointers left unused
@
depends on memcpy_rule3
@
identifier memcpy_rule3.ptr;
type VP, VP1;
@@

-VP ptr;
	... when != ptr;
? VP1 ptr;

// <smpl>

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

parent ca18f6ea

fs/btrfs/compression.c

+2 −4

Original line number	Diff line number	Diff line
		@@ -1231,7 +1231,6 @@ int btrfs_decompress_buf2page(const char *buf, unsigned long buf_start,
		unsigned long prev_start_byte;
		unsigned long working_bytes = total_out - buf_start;
		unsigned long bytes;
		char *kaddr;
		struct bio_vec bvec = bio_iter_iovec(bio, bio->bi_iter);

		/*
		@@ -1262,9 +1261,8 @@ int btrfs_decompress_buf2page(const char *buf, unsigned long buf_start,
		PAGE_SIZE - (buf_offset % PAGE_SIZE));
		bytes = min(bytes, working_bytes);

		kaddr = kmap_atomic(bvec.bv_page);
		memcpy(kaddr + bvec.bv_offset, buf + buf_offset, bytes);
		kunmap_atomic(kaddr);
		memcpy_to_page(bvec.bv_page, bvec.bv_offset, buf + buf_offset,
		bytes);
		flush_dcache_page(bvec.bv_page);

		buf_offset += bytes;

fs/btrfs/lzo.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -467,7 +467,7 @@ int lzo_decompress(struct list_head ws, unsigned char data_in,
		destlen = min_t(unsigned long, destlen, PAGE_SIZE);
		bytes = min_t(unsigned long, destlen, out_len - start_byte);

		kaddr = kmap_atomic(dest_page);
		kaddr = kmap_local_page(dest_page);
		memcpy(kaddr, workspace->buf + start_byte, bytes);

		/*
		@@ -477,7 +477,7 @@ int lzo_decompress(struct list_head ws, unsigned char data_in,
		*/
		if (bytes < destlen)
		memset(kaddr+bytes, 0, destlen-bytes);
		kunmap_atomic(kaddr);
		kunmap_local(kaddr);
		out:
		return ret;
		}

fs/btrfs/reflink.c

+1 −5

Original line number	Diff line number	Diff line
		@@ -103,12 +103,8 @@ static int copy_inline_to_page(struct btrfs_inode *inode,
		set_bit(BTRFS_INODE_NO_DELALLOC_FLUSH, &inode->runtime_flags);

		if (comp_type == BTRFS_COMPRESS_NONE) {
		char *map;

		map = kmap(page);
		memcpy(map, data_start, datal);
		memcpy_to_page(page, 0, data_start, datal);
		flush_dcache_page(page);
		kunmap(page);
		} else {
		ret = btrfs_decompress(comp_type, data_start, page, 0,
		inline_size, datal);

fs/btrfs/send.c

+2 −5

Original line number	Diff line number	Diff line
		@@ -4948,7 +4948,6 @@ static int put_file_data(struct send_ctx *sctx, u64 offset, u32 len)
		struct btrfs_fs_info *fs_info = root->fs_info;
		struct inode *inode;
		struct page *page;
		char *addr;
		pgoff_t index = offset >> PAGE_SHIFT;
		pgoff_t last_index;
		unsigned pg_offset = offset_in_page(offset);
		@@ -5001,10 +5000,8 @@ static int put_file_data(struct send_ctx *sctx, u64 offset, u32 len)
		}
		}

		addr = kmap(page);
		memcpy(sctx->send_buf + sctx->send_size, addr + pg_offset,
		cur_len);
		kunmap(page);
		memcpy_from_page(sctx->send_buf + sctx->send_size, page,
		pg_offset, cur_len);
		unlock_page(page);
		put_page(page);
		index++;

fs/btrfs/zlib.c

+2 −3

Original line number	Diff line number	Diff line
		@@ -432,9 +432,8 @@ int zlib_decompress(struct list_head ws, unsigned char data_in,
		PAGE_SIZE - (buf_offset % PAGE_SIZE));
		bytes = min(bytes, bytes_left);

		kaddr = kmap_atomic(dest_page);
		memcpy(kaddr + pg_offset, workspace->buf + buf_offset, bytes);
		kunmap_atomic(kaddr);
		memcpy_to_page(dest_page, pg_offset,
		workspace->buf + buf_offset, bytes);

		pg_offset += bytes;
		bytes_left -= bytes;